Photographic developer



patented 7, 1940 PATENT Fries PHOTOGRAPHIC DEVELOPER James R. Alburger, Merion, Pa., assignor to Radio Corporation of America, a corporation or Delaware No Drawing. Application April 30, 1938, Serial No. 205,363

36 Claims. (01. 95-88) This invention relates to photographic develdeveloper which will work without producing fog.

opers and methods of photographic development, and is, in part, a continuation of my application Serial No. 196,366, filed March 17, 1938, entitled Photographic Developer.

It has heretoforebeen customary to develop sound record negative film in ordinary positive developer or in a modification thereof, thereby.

producing a negative having the same relative characteristics as a picture positive or having these characteristics very slightly modified. This procedure has been highly undesirable, particularly with variable area sound records, where an extreme density of the exposed area is desired, together with complete freedom-from fog in the unexposed areas and strict proportionality of density'in .the area of graded exposure produced dueto the finite width of the exposure aperture adjacent to the exposedarea. 0 In addition to the foregoing, adeveloperfor this purpose must be satisfactory for use in the tanks of continuous developing machines; it

must have a relatively long life, i. e., must not age too rapidly; and it must maintain its developing action substantially constant during its period of usefulness.

Heretofore, no developer has been available having the foregoing characteristics. My improved developers have all of the foregoing characteristics and, in addition thereto, is extremely inexpensive, decreasing the developer cost, per foot of film, to only a small fraction of the previous cost.

In the preparation of my improved developer, I make use of the peculiar characteristic of certain metallic salts which permits them to act as a buffer and to maintain the effective alkalinity of the developer bath substantially con-. stant during its life. 40 One object of my invention isto provide an improved photographic developer. I

Another object of my invention is to provide an improved developer for sound track film.

Another object of my inventionis to provide an improved developer for sound track film of the variable area type.

Another object of my invention is to provide an improved high constant developer.

Another object of my invention is to provide a developer which will give a higher emulsion speed.

Another object of my invention is to provide a developer which will give 10w contrast for pic-L tures.

Another object of my invention is to provide a developer which will give a greatly increased latitude of exposure.

Another object of my invention is to provide a developer which will give a surface image.

Another object of my invention is to provide a developer which will produce a very uniform grain structure in the image.

Another object of my invention is to provide a developer which will prevent clumping of the silver grains.

a developer which has a lower change of development time with change in temperature than has heretofore been secured.

Another object of my invention is to provide a 30v developer, the exhaustion rate of which will be not greater than the rate of physical removal of the developing solution by the developed material whereby maintaining the developing solution at a constant volume will maintain it at a 35 constant developing power.

. Another object of my invention is to provide a developer which will develop each exposed silver grain in its entirety without adding thereto or subtracting therefrom. 40

Another object of my invention is to provide a developer which will develop the sensitive material to and beyond its gamma infinity.

Another object of my invention is to provide a developer which prevents softening of the gel- 45 atine by alkali.

Another object of my invention is to provide a developer which permits development at extremely high temperatures.

Another object of my invention is to harden emulsion material in an alkaline developer.

Other and incidental objects of my invention will be apparent to those skilled in the art from a reading of the following specification.

The objects are accomplished according to my invention by adding a metallic compound, such, for example, as potassium alum, to the developing solution, and using an alkali in sufficient quantity to dissolve or redissolve the precipitate which tends to be, or is, first formed.

My invention, in its broad aspect, is applicable to developers containing practically any of the usual developing agents which function in alkaline solution, and also is adapted to the use of any of the usual alkalies, although some developing agents and some alkalies are preferable to others.

For example, a very rapid developer is necessarily quite alkaline. proper buffering balance of the alum in this highly alkaline solution, it is accordingly necessary to use a large quantity of alum. Under this circumstance, if a sodium carbonate, for example, is used as alkali, the total solids in the solution become extremely great, in order to maintain the same constant alkalinity in the manner described in detail hereinafter, and I therefore prefer to use sodium hydrate.

Materials used Although I have above referred to the use of alum in developer, I find that a number of other materials may be used. The aluminum, for example, may be introduced in the readily available form of potassium aluminum sulphate, known generally as alum, or any other convenient water soluble aluminum salt may be used, such, for example, as aluminum sulphate, aluminum chloride, or aluminum bromide. Although aluminum is the metal which I have found to be usually most desirable for my purpose, I find that appropriate salts of either zinc, tin, chromium or lead i may also be used. These various metallic salts produce different degrees of effect with different developing agents, and, although I have found aluminum quite satisfactory with all developing agents which I have tried, some of the other metals produce too high or too low a reducing power to be generally satisfactory, although they are all operative with all the available developing agents. Lead salts, in general, appear to produce a somewhat unstable balance in the developer and increase the speed of development for any given developing agent quite considerably over that obtained with the other salts mentioned or with none of them. The chromium compounds are not as satisfactory as aluminumcompounds due to the instability of the chromium compounds produced in the developer which tend to precipitate out with them. Tin. and zinc vary.

the developing power with certain developers to a greater extent and with others to a lesser extent than the aluminum.

The aluminum compounds produce suflicient tanning action on the gelatine, or prevent the softening action of the alkali to such an extent,

In the preparation'of my improved developers,

I used somewhat less than the usual proportion of sodium sulphite for the reasons that, first, a large quantity of sulphite is not necessary and, second, the reduction in quantity of sulphite de-- creases the solution of silver salts and redeposi-" tion thereof which produces diffusion of the image in developers high in sulphite.

In order to produce a- In order to preclude any material effect upon the developer due to the production of alkali bromide in the solution during development, I prefer to initially provide in the solution such a quantity of bromide that further addition of bromide during the reactions causes no material change in the effect thereof. This effect of bromide is described in Theory of Development, by A. H. Nietz, published by the Eastman Kodak Co., Rochester, New York, and D. Van Nostrand Co., New York, 1922,'pages to 152. Optimum concentration for bromide to produce this constancy of effect is .08 mols. per liter.

The developing agent may be, so far as I have been able to ascertain, any usual or customary photographic developing agent. For example, the following developing agents have been satisfactory used with each of the aforementioned metals:

' sible substitutions in benzene derivatives is practically unlimited. Nuclear substitutions need be made such as in chlor-hydroquinone. Side chain substitutions need be made as in para-dimethylamino-phenol where methyl groups are substituted in the amino group. Side chain substitutions may be extended to the addition of further benzene rings. This is encountered in duratol. Another derivative related to duratol is para-dibenzyl-amino-phenol, where a double substitution is made in the amino group.

According to Theory of Development, (supra the effect of substitution" in the benzene derivatives used as developers have as their effect only the alternation of the energy of the organic reducing agent. Certain substitutions might make the developing energy so great that the compound would not be practical. Certain nitro -substitutions might do this. 'In general, substitu- Hydroxide Ethyl Halide Carboxyl Amino Benzene Methyl These groups may' be substituted 1148 5 or in combination. I

Tulu-hydroquinone (2 methyl-4-hydroxy-pheareaem Preparationof the developer Certain of the developing agents require different treatment to getthem into solution in the most suitable manner. For example, metol must be dissolved in water before sulphite is added. Hydroquinone must be protected by the presence of sulphite before sodium hydroxide is added, that is, for the best results. Duratol will not .dissolve without the presence of sodium hydroxide. These examples merely indicate that there is a variation in the properties of the various developing agents. Ingeneral, it is possible to dissolve the developing agent simultaneously with sodium hydroxide. Sodium sulphite is added to the solution, as is potassium bromide or a suit-.

The alum and alkali may, if desired, be dissolved separately and then mixed, or the alum may be dissolved first and the'alkali added afterward, or vice versa, according to which is most convenient. However, if sodium hydrate is used, the quantity thereof must be approximately the same as that of the alum, whereas if the carbonate is used, the quantity thereof must be of the order of four times the quantity of the alum,

depending upon the degree of hydration of the carbonate.

The developing agent may be mixed in a quantity amounting to approximately ,4 to gram molecular weight per liter. The amount of developer used is determined by the desired developer speed or reaction velocity. Sodium sul-- phite is added as a preservative in a quantity amounting to approximately mol. per litter or more. The concentration of sulphite is not critical, and should be not less than 1 molecule of sulphite for each molecule of developer.

Sodium hydroxide is, as pointed out above,

used as an energizer, and the quantity of this is determined by the characteristics desired in the developer. The usable concentrations range from below 10 grams per liter to above 300 grams per liter.

The sodium hydroxide is balanced with an appropriate amount of alum determined as follows: Powdered alum is slowly added to the solution containing hydroxide. As addition of the alum is continued, the rate of solution slowly decreases until the point is reached where further addition of alum produces no further solution, leaving undissolved alum crystals. Conversely, the alum may be dissolved first and the sodium hydroxide added later. In this case, the initial addition of sodium hydroxide produces a precipitate of aluminum hydroxide which is redissolved onfurther addition of sodium hydroxide, and when this precipitated aluminum hy-= any time during preparation thereof. The addition of other substances to the developing solution for other or" incidental purposes is within the scope of my invention provided only that the aforesaid balance between the aluminum content and alkali content is maintained.

Although I have described the preparation of a developer including alum, the same method is used in the preparation of a developer containing any of the other metals referred to.

The following formula illustrates a satisfactory composition which I have used:

NazSOa grams 50 Mono-methyl carboxyl paramino hydroxybenzene (glycine) grams 20 NaOI-I do 25 KAI(SO4)2- 12H2O do 30 Water to make ccs 1000 For maximum contrast with this developer, 10

' grams of potassium bromide should also be added.

Another example of the application of my invention in a developer which has been found useful is the following: I H y dr q u i n o n e 1 (para-dihydroxybenzene grams 15 NAzSOc do 17 KA1(SO4)212H2O d0 38 NaOl-I do 30 KBr do Water to make ccs 1000 The first of the above developer formulas, al-- though rather concentrated and therefore rather high in first cost, will, nevertheless, develop film of the type described at an extremely low cost. This is due to the fact that whereas the ordinary types of metol-hydroquinone developers heretofore used are effective for approximately 20 feet of film per liter of developer, with appropriate replenishment of the developer in the meantime,

my improved developer will serve to develop approximately 250 feet of film with the same loss proximately .2 in the density of the finished film.

As compared to the prior developers used on sound film which, with the customary exposure, would develop the film to a density of the order of 1.9, my improved developer will produce a density of approximately 2.1 on the sound'negative, and the sound prints can be exposed and developed to the correspondingly high density of 2.35 (as against 1.4) with a minimum of zero shift in the sound track, zero shift being the term applied to the shifting of the Z0 point of high frequencies in accordance with their amplitude, as described in the article entitled Modulated High Frequency Recording as a Means of Determining Conditions for Optimal Processing, by J10. Baker and D. H. Robinson, Journal of the Society of Motion Picture Engineers, volume 30, No. 1, January, 1938. Further, the high frequency loss, for

- example at 9000' cycles, with my developer is no greater at these high densities than at the lower densities attained with the prior art developers.

The film footage per literabove referred to is such that no replenishment of the developer is required in ordinary film developing machines.

The film runs through the machine at a speed of the pressure on this compressed air jet or blow back the rate of carry-over of the developer may,

Operation of the developer The reaction' of the organic, reducing agent with the exposed silver bromide in the film produces a shift in ion concentration through a long chain of reactions. When the developer is oxidized by silver bromide, Br- .ions are released. Aluminate ions exist from the reaction of It is understood that each and every compound indicated in the above reaction will form certain ions in solution. For example, the alum in solution would produce potassium ions, aluminum ions and sulphate ions. The sodium aluminate indicated would, in solution, produce sodium ions and aluminate ions. It is evident from the above reaction, which is really amass reaction balance consisting of three reactions, that there will be present in the solution a large number of different ions.

From chemical functions known to the art, it will be apparent that the above' reaction will reach a state of equilibrium depending on the molecular proportions of the several elements, tending in the direction indicated by the heavy arrows. Any change in alkalinity of the solution will shift the equilibrium point one direction or the other, depending on whether the alkalinity is increased or decreased. As indicated in the above reaction, if the alkalinity is decreased, the

equilibrium point will be shifted to the left.

The only thing that keeps the Al(OH)3 in solution is an excess of 'NaOH. The presence of Brions would shift the balance of the above reaction slightly to the left. Al(OH)3 is now better able to combine with the gelatineof the film to harden it, as in any tanning action. Thus the film (gelatine) in the near neighborhood of the developed image undergoes a pronounced hardening which is evidenced by a distinct lack of swelling of the gelatine.

As the supply of free alkali is converted into salts in course of development, free alkali is liberated by the aluminum-alkali compound or complex, thereby maintaining the alkalinity effectively constant. At the same time the aluminum hydroxide or other metallic hydroxide which is freed forms a gelatinous precipitate which entraps exhausted developing material and other foreign material which may be in the developer and carries all of this suspended material out of the solution in the manner well known in water purification by the use of aluminum salts. The developing solution is thereby maintained at all times free from the exhausted material which tends to form scum, spots, stains or fog on the film in the developers of the prior art.

This coagulation of aluminum and deleterious material may be either permitted to settle to the bottom of the developing container and removed therefrom at convenient intervals or the developer may be passed into a separate settling tank or container from which the sediment may be removed from time to time. Since the addition of fresh developer of the original composition does not tend to redissolve the aluminum as the addition of a stronger solution, such as generally used for enrichment of developer, would do, this precipitate does not tend to become'finely divided or; redissolved, and it is therefore readily removed from the zone of operations in the manner before described. This greatly decreases the cost of operation of developing-machines as compared to the present procedure wherein the developer is filtered under high pressure and through complicated filtering mechanisms in order to remove exhausted developing material. Of course, with my improved developer and method of development, a filter may be used if desired, but the filter required, due to the large size and gelatinous nature of. the material to be removed, is very much simpler than that required for removing the fine suspended particles from the usual commercial types of developer.

A further advantage of my improved developer is thatif the aforesaid gelatinous precipitate'is not removed, but is kept in suspension in the solution by mechanical agitation, either through the passage -of the film through a relatively small quantity of" solution or otherwise, this gelatinous precipitatedoes not show the tendency to adhere to the film, which is common to the materials in suspension in a partly exhausted developer of the usual type. In other words, a considerable portion of such material is removed from a developing machine by the blow-back and any residual material which may adhere to the film is easily removed in the rinse water, leaving no spots or stains whatever on the film.

It will be apparent from the foregoing that, in addition to a new developer, I have provided a novel method of removing foreign materials from the developer during the operation, a novel method of maintaining the developer at effectively constant alkalinity, and a novel method of maintaining the developer at constant effective developing properties.

I claim as my invention:

1. A photographic developer containing a developing agent, an alum, and sufiicient alkali to dissolvethe aluminum compound tending to be r precipitated by the alkali.

2. A photographic developer containing a developing agent, an aluminum salt, and sufiicient alkali to dissolve the aluminum compound tending to be precipitated by the alkali.

3. A photographic developer including a developing agent, .an alkaline sulphite, an alum, and sufficient alkali to maintain in solution the aluminum salts tending to be precipitated by the alkali..

4. A photographic developer including a developing agent, an alkaline sulphite, an aluminum alum, and suficient alkali to maintain in solution the aluminum compound tending to be. precipitated by the alkali. Y

5. A photographic developer including a developing agent and approximately equal portions of potassium alum and sodium hydrate.

6. A photographic developer including a developing agent, an alkali sulphite, and approxi mately equal portions of potassium .alum and sodium hydrate.

7. A developing solution containing 2. developing agent, the reaction products of an aluminum salt and an alkali, and a slight excess of alkali.

8. A developing solution containing a developing agent, the reaction products of an alum and an alkali, and a slight excess of alkali.

9. A photographic developer containing a phenolic developing agent, an aluminum salt, and sufiicient alkali to dissolve the aluminum salt tending to be precipitated by the alkali.

10. A photographic developer including a phenolic developing agent, an alkaline sulphite,

an alum, and suificient alkali to maintain in solution' the aluminum salts tending to be precipitated by the alkali.

11. A photographic developer including a phenolic developing agent and approximately equal portions of potassium alum and sodium hydrate, the weight of the alum slightly exceed ing the weight of the sodium hydrate.

12. A developing solution containing a phenolic developing agent, an alkali sulphite, the reaction products of an aluminum salt and an alkali, and a slight excess of alkali.

13. A photographic developer containing hydroquinone, an alum, and sufiicient alkali to dissolve the aluminum compound tending to be precipitated by the alkali.

14. A photographic developer containing hydroquinone, an aluminum salt, and sufiicient alkali to dissolve the aluminum compound tending to be precipitated by the alkali.

15. A photographic developer containing hydroquinone, an alkaline sulphite, an alum, and sufficient alkali to maintain in solution the aluminum salts tending to be precipitated by the alkali.

16. A photographic developer containing hydroquinone. an alkaline sulphite, an aluminum alum, and sufiicient alkali to maintain in solution the aluminum compound tending to be precipitated by the alkali.

17. A photographic developer including hydroquinone, and approximately equal portions of potassium alum and sodium hydrate.

18. A photographic developer including hydroquinone, an alkali sulphite,.and approximately equal portions of potassium alum and sodium hydrate.

l9. A developing solution containing hydroquinone, the reaction products of an aluminum salt and an alkali, and a slight excess of alkali.

20. A developing solution containing hydroquinone, the reaction products of an alum and an alkali, and a slight excess of alkali.

21. A photographic developer containing Glycine, an alum, and suflicient alkali to dissolve the aluminum compound tending to be precipitated by the alkali.

22. A photographic developer containing Glycine, an aluminum salt, and sufficient alkali to dissolve the aluminum compound tending to be precipitated by the alkali.

23. A photographic developer including Glycine, an alkaline sluphite, an alum, and sufiicient alkali to maintain in solution the aluminum salts tending to be precipitated by the alkali.

24. 'A photographic developer including Glycine, an alkaline sluphite, an aluminum alum, and sufiicient alkali to maintain in solution the aluminum compound tending to be precipitated by the alkali.

25. A photographic developer including Glycine and approximately equal portions of potassium alum and sodium hydrate.

26. A photographic developer including Glycine, an alkali sulphite, and approximately equal portions of potassium alum and sodium hydrate.

27. A developing solution containing Glycine, the reaction products of an aluminum salt and an alkali, and a slight excess of alkali.

28. A developing solution containing Glycine, the reaction products of an alum and an alkali, and a slight excess of alkali.

29. A photographic developer containing Duratol, an alum, and sufficient alkali to dissolve the aluminum compound tending to be precipitated by the alkali.

30. A photographic developer containing Duratol, an aluminum salt, and sufiicient alkali to dissolve the aluminum compound tending to be precipitated by the alkali.

31. A photographic developer including Duratol, an alkaline sulphite, an alum, and suflicient alkali to maintain in solution the aluminum salts tending to be precipitated by the alkali.

'32. A photographic developer including Duratol, an alkaline sulphite, an aluminum alum, and

sufiicient alkali to maintain in solution the alumi- JAMES R. ALBURGER CERTIFICATE OF CORRECTION. Patent No. 2,199,901;. I v May 7 ,1 191m. v "JAMES R. ALBURGER.

It ishereby certified that error appears in the printed specification of the above numbered; patent requiring correction as follows: Page 5, sec- 0nd column', lines 6 and 10, claims 25 and. 2!; respectively, for "sluphite" read sulp'hite-; and that: the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed. and sealed this 2nd day of Ju1y,.A. -D. 191m.

Henry Van Arsdal'e, (Seal) 7 Acting Commissioner of Patents. 

